Is there a way to disarm the anti-theft system?

Your problem is likely the pats collar or module and you can figure it out by using the following process:
1. Insert key and turn to the run position without starting.
2. Wait 2 to 3 minutes until the light stops blinking fast.
3. Count the blink pattern (in most cases it will be a code 15 which is 1 blink followed by a short pause then 5 blinks followed by a pause then repeating a code 15 is usually caused by a bad ground in the system or a bad transceiver or transponder).